With one of the two Boston bombing suspects killed in a shootout and the other the subject of a massive manhunt, PEOPLE spoke with their shocked father, Anzort Tsarnaev, and their sister, Alina Tsarnaeva, on Friday morning.

"They never could have done this. Never, ever, ever!" Tsarnev told PEOPLE via phone from Russia. In a conversation filled with screaming and yelling, he was clearly in a state of disbelief and horrified by the events he watched unfold on TV.

The two suspects now implicated in the Boston Marathon bombing are brothers – one has been killed in a shootout and the other is now on the run – and they have family on the East Coast.

"These are my nephews! My brother's sons!" their stunned uncle Ruslan Tzami told PEOPLE from his home in Maryland on Friday morning, just a short time after the two men's likenesses and names were revealed.

Tzami wept as he spoke of the brothers who emigrated from Kyrgyzstan in 2001: Tamerlan Tsarnaev, 26, was born in Russia. Dzhokhar Tsarnaev, 19, was born in Kyrgyzstan, is in possession of a Massachusetts drivers license and is on the run. He "wanted to be a doctor," said the uncle.

One of two suspects in the Boston Marathon bombings is dead after the killing of a university officer and a shootout with police, and a massive manhunt is underway for the other, authorities said early Friday.

Police have locked down some neighborhoods in Boston and its western suburbs as they search for the remaining suspect, who is known as Dzhokhar Tsarnaev, or the man in the white hat from marathon surveillance footage.

The dead suspect was identified as Tamerlan Tsarnaev, 26, born in Russia and the brother of Dzhokhar. Anzor Tsarnaev, the father of the suspects, claims that his son who is still on the loose is a smart and accomplished young man.

"My son is a true angel," he told The Associated Press by telephone from the Russian city of Makhachkala on Friday. "Dzhokhar is a second-year medical student in the U.S. He is such an intelligent boy. We expected him to come on holidays here."

The FBI has released photos of two suspects in the Boston Marathon bombings and is asking for the public's help in identifying them, zeroing in on the two men on surveillance-camera footage less than three days after the deadly attack.

FBI Agent Richard DesLauriers says the photos came from surveillance cameras, photos and other evidence near the explosion sites. One man is seen wearing a light-colored baseball cap, the other a dark cap. The man in the dark cap set down a backpack at the site of one of the blasts, DesLauriers said.

Within moments of the announcement, the FBI website crashed, perhaps because of a crush of visitors.